Abstract
Polyphenols derived from tea are thought to be important for human health. We show using a combination of particle tracking microrheology and small-angle neutron scattering that polyphenols acts as cross-linkers for purified gastrointestinal mucin, derived from the stomach and the duodenum. Both naturally derived purified polyphenols, and green and black tea extracts are shown to act as cross-linkers. The main active cross-linking component is found to be the galloylated forms of catechins. The viscosity, elasticity and relaxation time of the mucin solutions experience an order of magnitude change in value upon addition of the polyphenol cross-linkers. Similarly small-angle neutron scattering experiments demonstrate a sol-gel transition with the addition of polyphenols, with a large increase in the scattering at low angles, which is attributed to the formation of large scale (>10 nm) heterogeneities during gelation. Cross-linking of mucins by polyphenols is thus expected to have an impact on the physicochemical environment of both the stomach and duodenum; polyphenols are expected to modulate the barrier properties of mucus, nutrient absorption through mucus and the viscoelastic microenvironments of intestinal bacteria.
Highlights
In recent years there has been growing evidence regarding the beneficial effects on human health of chemicals synthesized in plants called polyphenols, in particular their anti-oxidant properties [1,2]
2.2 Particle Tracking Microrheology (PTM) Lyophilised mucins were solubilised in a 10 mM phosphate buffer at pH 7 and after equilibrium was reached (48 hrs) they were treated with lyophilised polyphenols or tea extracts
The viscosity, elastic shear modulus and the resulting relaxation times of the aforementioned solutions are shown in Table 1 (SI text)
Summary
In recent years there has been growing evidence regarding the beneficial effects on human health of chemicals synthesized in plants called polyphenols, in particular their anti-oxidant properties [1,2]. Polyphenols are secondary metabolites and are divided into several classes depending on the number of phenol rings they contain and the structural elements that connect these rings, e.g. flavonoids, phenolic acids, stilbenes and lignans [3]. Catechin (C) and its isomer epicatechin (EC) are the most abundant phenolic molecules found in many types of fruit as well as in red wine and tea [4]. Gallates of epicatechin such as epigallocatechin (EGC) and epigallocatechin gallate (EGCG) are predominantly found in green and black tea, and are differentiated from catechins with respect to the fact that there is at least one gallate ring present in their structure [5]
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